Liquid scintillation, counting and compositions

ABSTRACT

The emissions of radioactive isotopes in both aqueous and organic samples can be measured by liquid scintillation counting in micellar systems. The micellar systems are made up of scintillation solvent, scintillation solute and a mixture of surfactants, preferably at least one of which is relatively oilsoluble water-insoluble and another which is relatively watersoluble oil-insoluble.



1. IN A PROCESS FOR COUNTING IN LIQUID SCINTILLATION COUNTING DEVICES USING LIQUID SCINTILLATION COUNTING MEDIUM CONTAINING SURFACTANT; THE STEP COMPRISING FORMING THE MEDIUM BY ADMIXING AN AMOUNT OF AT LEAST ONE OF SCINTILLATION SOLVENT AND SCINTILLATION SOLUTE SUFFICIENT O ABSORB EMISSION FROM ISOTOPES AND RADIATE THE ABSORBED ENERGY AT DEVICE-DETECTABLE LEVELS WITH AN AMOUNT OF A PLURALITY OF DIFFERENT SURFACTANTS SUFFICIENT TO IMPART THERMODYNAMIC STABILITY TO THE RESULTING MEDIUM ON ADDITION OF SAMPLE AND DURING WHICH COUNTING REACTS TO PROVIDE ESSENTIALLY NO FLUORESCENCE, CHEMILUMINESCENCE OR PHOSPHORESCENCE, THE PLURALITY OF SURFACTANTS BEING SELECTED FROM THE GROUP CONSISTING OF A. A COMBINATION OF PREFERENTIALLY OIL-SURFACTANT; AND PREFERENTIALLY WATER-SOLUBLE SURFACTANT; FACTANT; C. A COMBINATION OF CATIONIC AND NONIONIC SURFACTANT; AND D. A COMBINATION OF SURFACTANT WHICH ACTS AS A DISPERSANT AND SURFACTANT WHICH ACTS AS A SURFACE-TENSION REDUCING AGENT;
 2. The process of claim 1 wherein the micellar system includes a cosurfactant.
 3. The process of claim 1 wherein a scintillation solvent sufficient to dissolve any undissolved scintillation solute is admixed with the micellar system and scintillation solute.
 4. The process of claim 1 wherein a secondary scintillation solute is admixed with the micellar system and scintillation solute.
 5. A micellar liquid scintillation counting composition comprising scintillation solute in small amounts effective to provide countable scintillation in the composition on addition of radioactive sample to the composition, scintillation solvent in amounts effective to permit interaction between the scintillation solute and emissions from the radioactive sample on addition of radioactive sample to the composition, and a plurality of surfactants selected from the group consisting of a. a combination of preferentially oil-soluble surfactant and preferentially water-soluble surfactant; b. a combination of anionic surfactant and nonionic surfactant; c. a combination of cationic and nonionic surfactant; and d. a combination of surfactant which acts as a dispersant and surfactant which acts as a surface-tension reducing agent the surfactants being present in an amount in excess of that amount required to render the mixture thermodynamically stable and to reduce the vapor pressure of the dispersed phase liquid, the surfactants, scintillation solute, and scintillation solvent being substantially inert with regard to chemical reactivity or energy transfer which results in chemiluminescence, fluorescence, or phosphorescence.
 6. The medium of claim 5 wherein the medium contains cosurfactant.
 7. The medium of claim 5 comprising a higher molecular weight fatty acid, relatively water-insoluble alcohol, relatively water-soluble lower molecular weight alcohol and n-isoalkyl phenol polyethoxyethanol.
 8. The medium of claim 5 comprising about 25% higher molecular weight fatty acid, about 25% n-hexanol, about 15% isopropanol, about 22% isooctylphenol-polyethoxyethanol, and aqueous NaOH to volume at a pH of about
 7. 9. the medium of claim 5 comprising about 29% higher molecular weight fatty acid, about 28% n-hexanol, about 18% isopropanol, and about 25% isooctylphenol-polyethoxyethanol.
 10. The medium of claim 5 comprising about 38% sodium dihexyl-sulfosuccinate, about 5% isopropanol, about 52-53% isooctylphenol-phenoxy polyethoxyethanol, and 4.8% water. 